I shot the following picture with a Canon AE-1 Program on a roll of Ilford HP5 400 (I pushed the roll to 800). I developed it using Ilfosol 3 and scanned it with Epson scanner V370. As you can see, there are - I'm not sure how to describe them - smudge like shadows corresponding to the perforations. The shadows are only on the third frame of the roll. I am left to wonder what caused these on only one frame, and what can I do in the future to prevent it from happening?

Smudges on film perforations

The effect is even easier to see on the negative:

Negative roll


2 Answers 2


It's called "light piping" and it is due to some minor/cumulative light leak/exposure. Films with a polyester base are more prone to it, as is B&W positive film.

The only thing you can do to minimize the potential of occurrence is to store the film with as little exposure to light as possible (before loading and after exposure).



As this pattern appears on a thin (underexposed) frame of the roll, I think it is due to slight over agitation in processing. The marks are characteristic of 35mm film over agitation.

Carefully inspect the rest of the roll and you will see the same effect on other frames coinciding with the sprocket holes.

The sprocket holes increase the flow of developer more than the unperforated edges due to a venturi effect.

  • \$\begingroup\$ Reviewing the film, I notice a (albeit less pronounced) pattern on frame 1, and much less noticeable patterns on frames 8 and 10 (only on sprocket perforations - no bleeding into the image). I used a paterson tank, and the earlier frames were closer to the hub of the spool. For agitation, I used the spindle widget (as I usually do) that comes with the tank rather than up ending the tank. \$\endgroup\$ Jun 12, 2021 at 21:31
  • \$\begingroup\$ I am very careful with the timing of the agitation ( I use the MassiveDev app for timing). I have developed the same film shot at same speed before, and this did not happen. Is it due to how vigorous the agitation motion is? \$\endgroup\$ Jun 12, 2021 at 21:34
  • \$\begingroup\$ @BolucPapuccuoglu Yes. You should also be aware that every different combination of film and developer react differently together. The amount of density can make the effect more or less evident. Processing agitation is a big deal — especially with 35mm film. Pushing increases the contrast. As you gain experience (with that film/developer combination) you'll find an optimal degree of agitation — all other things being equal. Good luck \$\endgroup\$
    – Stan
    Jun 12, 2021 at 23:05
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    \$\begingroup\$ How can you overdevelop an area that was not exposed to light (the edges of sprocket holes)? Overdevelopment causes exposed areas of the negative to become more dense (increases contrast); but it cannot do anything to unexposed areas. Without exposure to light, the silver halides have not undergone the chemical transformation to create a latent image... \$\endgroup\$ Jun 13, 2021 at 15:14
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    \$\begingroup\$ @StevenKersting I think you deserve +1 for the answer you gave. As I was about to "explain" how, I noticed that the edge above the sprocket holes is indeed fogged indicating your answer concerning light piping as the cause of the effect is correct. My answer was wrong. Good work. \$\endgroup\$
    – Stan
    Jun 13, 2021 at 17:25

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